1. Field of the Invention
The present invention relates to an imaging apparatus which, in order to grasp the status of a road, images an object using a plurality of CCDs to detect an obstacle and the like on the road, and a distance measurement apparatus for calculating the distance between the car and the object.
2. Description of the Related Art
In recent years, with the increasing interest in the automobile safety, the demand of being able to drive a car while keeping a safe distance between the car and a car travelling ahead, as well as the demand for an apparatus which can detect in advance an obstacle and the like on a road and urge the driver to avoid the obstacle, have increased and will further increase. In order to satisfy these demands, it has been started to observe the road ahead of his or her car using an imaging apparatus.
A conventional distance measurement apparatus is described in Japanese Laid-Open Publication No. 8-75454, for example. This conventional distance measurement apparatus will be described with reference to FIG. 12.
Referring to FIG. 12, the conventional distance measurement apparatus includes imaging elements 102, 103, and 104, half mirrors 105 and 106, and an image processing element 107.
The operation of the conventional distance measurement apparatus with the above configuration will be described. The distance measurement apparatus images an object 101 using the imaging elements 102, 103, and 104 so that the horizontal or vertical parallax between the adjacent imaging elements constitutes several pixels. The image processing element 107 receives a plurality of imaged video signals simultaneously to synthesize video signals on the same horizontal or vertical lines among the plurality of video signals and thus to produce an image for parallax detection. Using the produced image for parallax detection, the parallax is obtained from the tilt of a straight line formed by points corresponding to the edges of the object 101, and then the distance between the car and the object 101 is calculated based on the parallax.
The conventional distance measurement apparatus with the above configuration is disadvantageous in the following points. Since the conventional distance measurement apparatus includes a plurality of imaging elements, the following problems arise. It is not easy to accommodate such an apparatus in a small space inside a car. Two optical systems are required, increasing the production cost. The resolution of each pixel is as small as about 50 cm for an object located about 100 m distant from the car, which fails to provide a sufficient distance measurement performance. The plurality of optical systems need to be aligned with one another with high precision, resulting in the difficulty in adjustment and an increase in maintenance cost.